FRICTION.
It is a spirited sight to watch the operation of sharpening tools upon a grindstone or emery wheel run by steam. Showers of sparks are produced by the friction. We often observe the same phenomenon when the brakes are applied to rapidly revolving car wheels. Rails are heated by the friction of the passing train. You may have had the misfortune, while riding, to have one of your carriage wheels become set, caused by the box of the hub, and the axle becoming so heated by friction as to “unite” their surfaces. All machinery requires constant watching and lubrication to prevent undue friction and serious wearing.
Mills have not unfrequently been set on fire by rapidly revolving belts coming in contact with the woodwork. When the whale, frantic with the pain of the harpoon, darts away with lightning speed, the sailors are compelled to dash water over the spinning wheel on which the rope is wound.
In all these instances motion is transformed into heat.